Screen recording is an essential tool for sharing what's on our smartphones. If you want to send your friends and family an unsharable video you're watching or a cool trick you discovered on your phone, recording your screen is one way to do so. Messenger, Facebook's standalone chat app, is looking to simplify the experience by implementing screen sharing directly in your video calls.
Unfortunately, screen sharing isn't available at this time. In fact, it's most likely still in early development. If we thought you'd be able to test out the feature by signing up for Messenger's beta on iOS or Android, we would suggest doing so. However, we only know about Facebook's plans thanks to Jane Manchun Wong.
Wong is an app researcher who dives into an app's coding to find upcoming features. Screen sharing is just her latest discovery. Wong reports the function is called "Share Your Screen Together" and is located in Messenger's Video/Audio call screen. When activated, your camera will turn off, switching focus to your iPhone or Android's display. You can leave the app to show off anything on your phone, as demonstrated by Wong opening Instagram in one of her screenshots:
As this feature is so new, Facebook may never release it to the public. However, screen sharing would be a fantastic addition to an app used by so many to share just about everything else in their lives. It would only make sense for Facebook to publish the feature after enough development eventually. Until then, if you absolutely need to screen share over a call, Skype already has the capabilities to let you do so.